The use of ophthalmic lenses for the correction of ametropia is well known. For example, multifocal lenses, such as progressive addition lenses (“PAL's”), are used for the treatment of presbyopia. The progressive surface of a PAL provides far, intermediate, and near vision in a gradual, continuous progression of vertically increasing dioptric power from far to near focus, or top to bottom of the lens.
PAL's are appealing to the wearer because PAL's are free of the visible ledges between the zones of differing dioptric power that are found in other multifocal lenses, such as bifocals and trifocals. However, an inherent disadvantage in PAL's is that, due to the incorporation of the power for the near vision zone, the lens' center thickness is increased in comparison to single vision lenses. This makes the PAL less desirable from a cosmetic standpoint to the lens wearer.
One method used to decrease the center thickness of PAL's is to form the lens from a high refractive index material to reduce the sagittal height of the lens. Useful high refractive index materials include certain plastics. Additionally, aluminosilicate or borosilicate glass doped with certain rare earth metals provides a high refractive index material. However, a need exists for alternatives to these methods to reduce the center thickness of a multifocal lens
FIG. 1 depicts a cross-sectional view of a lens 10 made according to the method of the invention. High index, inorganic material layer 12 is deposited onto substrate 11. Inorganic material 112 includes an intermediate vision zone 13 and a near vision zone 14. In FIG. 2 is epicted a lens 20, a second embodiment of the invention in which the inorganic material is deposited so as to form a refractive index modulation.